1. Field of the Invention
The invention relates to a wireline method and apparatus for sealing a well casing having a length of smaller diameter production tubing therein, including a bridge plug, and components therefor, which is passable through the production tubing and into the well casing.
2. Description of the Prior Art
In the production of hydrocarbons, it is typical to provide a casing within the borehole and to perforate the casing along its length adjacent a particular formation which contains the hydrocarbons to be produced. Typically, production tubing is disposed within the casing and the production tubing is sealed within the casing as by a conventional packer. The hydrocarbons then flow from the producing formation through the perforations in the well casing and upwardly to the surface via the production tubing.
Frequently, a particular formation, from which hydrocarbons had previously been flowing, ceases to flow the desired hydrocarbons, but rather undesired fluids, such as water, begin to flow into the casing. If another formation exists adjacent the casing, such formation being located above the first formation which is now flowing undesired fluids, the casing is sealed above the first group of perforations. Thereafter the casing is again perforated along its length adjacent the second formation from which hydrocarbon fluids are desired to be produced.
Although many devices exist which can be utilized to seal a well casing, and can be readily passed through the well casing to the desired location along the well casing, most of these devices cannot pass through conventional production tubing because of their size. Thus, in order for these conventional devices to be utilized in the previously described situation of a producing well having production tubing therein, it is necessary to remove the production tubing in order to use such devices to seal off a section of the well casing. This is a costly and time consuming operation, the cost and time increasing proportional to the depth of the well and the length of the production tubing. Furthermore, conventional devices require a work-over rig to be installed at the well site, which results in considerable delay and expense.
Two wireline suspended devices have previously been proposed to seal a well casing, such devices being capable of first passing through the production tubing disposed within the well casing. One of these devices is a collapsible metal petal basket which is lowered through the production tubing and into the well casing to the desired depth where the casing is to be sealed. At that point within the well casing, the petals of this device are caused to swing outwardly into engagement with the well casing. Gravel and/or sand are then passed through the production tubing and land on top of the metal petal basket. Thereafter, cement is poured on top of the gravel and/or sand. Upon curing of the cement, a cement plug is provided at the desired depth in the well casing. The disadvantages of utilizing this device are that it typically takes a long period of time for the cement to properly cure. Since the undesired fluids flowing in the well casing beneath the cement may be still flowing, and are frequently flowing under substantial pressure, the cement does not cure properly and/or the integrity of the seal between the cement and the well casing is not of the quality which is desired due to a high differential pressure acting upon the cement, as well as from the roughened and contaminated surface conditions of the well casing due to corrosion, sludge, paraffin, and/or carbonate. Additionally, the time required from the start of the cement plugging process until the well can be placed back into service can be excessive and often very expensive.
Another device which has been utilized to provide the desired sealing of a well casing and which can be passed through the production tubing is an inflatable rubber bladder. This bladder is placed at the desired depth where the seal is to be placed within the well casing, and the bladder is then inflated. Typically, the bladder is of thin-wall construction to facilitate its passage through the tubing and its inflation. After the bladder has been inflated, cement is poured over the bladder and the desired sealing is effected upon the cement curing. The disadvantages with this device are that because of the pressure and temperature conditions existing down-hole, as well as the roughened and contaminated surface conditions of the well casing previously described, the bladder frequently ruptures upon being inflated, or ruptures after the cement has been poured upon the bladder, but before the cement has cured. Thus, it is necessary to start over to attempt the sealing procedure. Further, some of these bladder devices have been provided with a vent tube about which the bladder is secured. This vent tube is utilized to relieve pressure from below the bladder until such time as the cement has sufficiently cured. After the cement has cured, the vent tube is then sealed off. Frequently, the diameter of the vent tube is not large enough to supply the necessary pressure relief, whereby the rubber bladder frequently bursts due to the excessive pressure build-up exerted upon the rubber bladder.
Accordingly, prior to the development of the present invention, there has been no method and/or apparatus for sealing a well casing, which: is first passable through production tubing to the desired depth in the well casing; is not subject to damage during installation; is not dependent upon cement which must be cured in order to provide the desired sealing; provides 100% seal integrity; can withstand high temperature and pressure conditions; is economical to manufacture and use; and quickly provides the desired sealing. Therefore, the art has sought a method and apparatus for sealing a well casing which is: passable through production tubing; does not require the use of cement; provides high quality seal integrity; is efficient to manufacture and use; does not require excessive time to provide the desired sealing; can withstand high pressure and temperature conditions; and is not readily subject to damage while being utilized.